Support more formats for image download

[huiwanpnnl]

@jourdain, a colleague from the E3SM atmosphere group asked whether we could support additional formats for image download. Let's discuss this in one of our meetings.

[huiwanpnnl]

Close for now until.

[huiwanpnnl]

Reopen issue, because we were asked again about this by a different colleague. Should follow up.

[huiwanpnnl]

When2Meet poll for selecting a time to meet and further discuss this: https://www.when2meet.com/?37920342-T5XGc

[huiwanpnnl]

@jourdain and I had a meeting with Oscar today and clarified many points. While the agreement was to not add the capability to allow specification of resolution (e.g., dpi) or format (png, pdf, etc.), I realized it would be useful to update our website to include the following:

• a brief explanation of the fact that the buttons, text, and color bars in the UI come from trame through the browser, while the visualization originates from ParaView;
• a brief discussion of the implication of this separation;
• a suggestion of using state files to save contour settings, allowing changes of viewport layout at a later point for image export for presentations, papers, etc.